Portable solar-heating system having an inflatable solar collector

ABSTRACT

A solar-heating system having an inflatable solar collector connected to a housing that can be installed, e.g., in a sash window of a house. The housing has an air blower that draws air from the interior of the house and directs it into the inflatable solar collector, which is positioned outside the window. The collector has a flexible permeable membrane that serves as a transpired absorber of solar radiation. The air flowing through the collector is heated when it percolates through the membrane exposed to solar light. The heated air is returned back to the interior of the house, thereby providing space heating. In certain embodiments, in addition to serving as a transpired absorber, the membrane can also serve as an air filter that removes particles, odor-causing pollutants, and/or allergens from the drawn air.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/107,738 filed on Oct. 23, 2008, and entitled“Portable Solar Heating Apparatus for Window Installations Having anInflatable Solar Collector,” which is incorporated herein by referencein its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to solar-energy utilization and, morespecifically, to solar-heating systems.

2. Description of the Related Art

This section introduces aspects that may help facilitate a betterunderstanding of the invention(s). Accordingly, the statements of thissection are to be read in this light and are not to be understood asadmissions about what is in the prior art or what is not in the priorart.

Heating, ventilation, and air conditioning (HVAC) systems account forabout one half of the energy used in residential buildings in the UnitedStates. Solar HVAC technologies can be used to offset at least a portionof this energy. The U.S. Energy Information Administration (EIA)classifies solar-heating systems into three categories: low-, medium-,and high-temperature systems. Low-temperature systems are usually usedto heat swimming pools and for space heating. Medium-temperature systemsusually generate hot water for residential and commercial use.High-temperature systems concentrate sunlight using mirrors and/orlenses and are generally used for generating electricity.

A typical household solar-heating system is a low- or medium-temperaturesystem that has a solar collector, with a heat-transfer fluid (e.g., airor water) flowing through the collector to absorb solar-generated heatand transport it to a storage or distribution subsystem (e.g., a hotwater tank or heat radiator). The solar collector is usually placedwhere solar-radiation levels are relatively high, e.g., on the roof ofthe house. A pump circulates the heat-transfer fluid through the solarcollector and storage/distribution subsystem, thereby transporting theheat to the place of its intended use.

An important consideration for the individual consumer is the cost andease of deployment of the solar-heating system. For example, arelatively expensive solar-heating system has a relatively long pay-backperiod, which makes it unattractive to the consumer. A solar-heatingsystem that is permanent or difficult to deploy might similarly beunattractive because the consumer might prefer to have it deployed onlywhen needed, e.g., during the winter months, and have it removed whennot needed, e.g., during the periods of hot weather.

SUMMARY

Disclosed herein are various embodiments of a solar-heating systemhaving an inflatable solar collector connected to a housing that can beinstalled, e.g., in a sash window of a house. The housing has an airblower that draws air from the interior of the house and directs it intothe inflatable solar collector, which is positioned outside the window.The collector has a flexible permeable membrane that serves as atranspired absorber of solar radiation. The air flowing through thecollector is heated when it percolates through the membrane exposed tosolar light. The heated air is returned back to the interior of thehouse, thereby providing space heating. In certain embodiments, inaddition to serving as a transpired absorber, the membrane can alsoserve as an air filter that removes particles, odor-causing pollutants,and/or allergens from the drawn air. Advantageously, inflatable solarcollectors of the invention can be manufactured using inexpensive,durable, and readily available materials. The collectors are inherentlyresilient to impact and shock, relatively easy to deploy and remove asneeded, easy to adjust to the surrounding terrain and secure at adesired tilt angle, and easy to clean.

According to one embodiment, provided is a system having (i) a housingwith an air-intake register and an air-exhaust register and (ii) aninflatable solar collector operatively connectable to the housing. Thehousing has an air blower configured to draw air through the air-intakeregister and direct the drawn air into a tube connectable to theinflatable solar collector. The inflatable solar collector has a firstchamber and a second chamber separated by a flexible permeable membrane.In operation, air pressure generated by the air blower causes the drawnair to flow through the tube into the first chamber, percolate throughthe permeable membrane into the second chamber, and exhaust from thesecond chamber through the air-exhaust register.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and benefits of various embodiments of theinvention will become more fully apparent, by way of example, from thefollowing detailed description and the accompanying drawings, in which:

FIGS. 1A-B show diagrammatic views of a solar-heating system accordingto one embodiment of the invention;

FIGS. 2A-D show diagrammatic views of a housing that can be used in asolar-heating unit of the solar-heating system shown in FIG. 1 accordingto one embodiment of the invention;

FIGS. 3A-B show perspective three-dimensional views of an inflatablesolar collector that can be used in a solar-heating unit of thesolar-heating system shown in FIG. 1 according to one embodiment of theinvention;

FIGS. 4A-E schematically show representative flexible permeable layersthat can be used to form a flexible permeable membrane for theinflatable solar collector of FIG. 3 according to various embodiments ofthe invention;

FIGS. 5A-B show perspective three-dimensional blow-up views of variousairflow-distribution components that can be used in the inflatable solarcollector of FIG. 3 according to one embodiment of the invention; and

FIGS. 6A-B schematically show an airflow pattern in an inflatable solarcollector of a solar-heating unit according to one embodiment of theinvention.

DETAILED DESCRIPTION

FIGS. 1A-B show diagrammatic views of a solar-heating system 100 havingtwo substantially analogous solar-heating units 102 a and 102 baccording to one embodiment of the invention. More specifically, FIG. 1Ashows each of solar-heating units 102 a and 102 b deployed at theexterior of a structure (e.g., a house) 150. FIG. 1B shows an enlargedcross-sectional view of a portion of solar-heating unit 102 a. Althougheach of solar-heating units 102 a and 102 b can be deployed at anysuitable location adjacent to structure 150, a location that canmaximize the amount of solar energy collected by the solar-heating unit,such as a wall 152 with a southern exposure (in the NorthernHemisphere), is generally preferred.

Solar-heating unit 102 has a housing 110 and an inflatable solarcollector 120 that is operatively connected to the housing. In general,housing 110 can be mounted in any suitable opening in a wall or roof ofstructure 150. For example, housing 110 a of solar-heating unit 102 arests on the lower windowsill of a first-floor window 154 a and issecured in place by a sliding sash 156, which is pushed down against anupper side 112 of the housing (see FIG. 1B). Housing 110 b ofsolar-heating unit 102 b is similarly secured in a second-floor window154 b.

Collector 120 a of solar-heating unit 102 a is deployed in a tiltedposition. More specifically, side rings or hooks 122 of collector 120 aare attached to tethers 118 a, with each of the tethers being tightlyextended between a respective anchor 114 (see FIG. 1A) and a respectivering 108 of housing 110 a (see FIG. 1B). Anchors 114 are hammered intothe ground to form a desired angle between tethers 118 a and theexterior surface of wall 152, which causes collector 120 a to beoriented at that angle with respect to that surface.

Collector 120 b of solar-heating unit 102 b hangs vertically, under itsown weight, from housing 110 b (FIG. 1A). Tethers 118 b, which aresimilar to tethers 118 a, are loosely connected to a wall hook 116,e.g., to prevent excessive flapping of collector 120 b in wind gusts.One skilled in the art will understand that other suitable arrangementsfor mounting/securing housing 110 and/or collector 120 can similarly beused in other embodiments of the invention.

Inflatable solar collector 120 relies on internal air pressure tomaintain its shape. When depressurized and deflated, collector 120 canbe rolled up or folded to occupy a relatively small volume. In oneembodiment, housing 110 has a compartment 140 that can be used to storecollector 120 in a deflated state.

Housing 110 has an electrical air blower 130 (see FIG. 1B) whose powercord 132 can be plugged into an electrical outlet, e.g., insidestructure 150. In operation, air blower 130 draws air from the interiorof structure 150 and directs the drawn air into collector 120, therebyinflating it. The air flows through various chambers of collector 120and is then exhausted back into the interior of structure 150. Whencollector 120 is exposed to solar radiation, the air flowing through thecollector is heated up, which causes the heated air to transport thesolar-generated heat from the collector to the interior of structure150, thereby providing space heating.

FIGS. 2A-D show diagrammatic views of a housing 200 that can be used ashousing 110 (FIG. 1) according to one embodiment of the invention. Morespecifically, FIG. 2A shows a front view of housing 200, whichcorresponds to a view, e.g., from the interior of structure 150 (alsosee FIG. 1B). FIG. 2B shows a top cross-sectional view of housing 200.FIGS. 2C-D show side cross-sectional views of housing 200 correspondingto planes CC and DD, respectively, shown in FIG. 2B.

Referring to FIG. 2A, a front panel 206 of housing 200 has an air-intakeregister 202 for drawing air, e.g., from the interior of structure 150,and an air-exhaust register 204 for returning the air heated in thesolar collector (e.g., collector 120, FIG. 1) back to the interior ofthe structure. In one embodiment, one or both of registers 202 and 204have adjustable shutters 205 that can be used, e.g., to shut off theregisters or to regulate the volume/direction of the air intake/exhaust.

Front panel 206 further has a control module 210 for controlling theoperation of the solar-heating unit. Control module 210 has atemperature-control knob 212 that can be used to set a target roomtemperature. One or more temperature sensors (not explicitly shown inFIG. 2) located in housing 200 and/or in the solar collector coupled tothe housing provide the corresponding temperature readings for controlmodule 210. Based on the temperature setting and the temperaturereadings, control module 210 can turn ON and OFF an air blower or pump230 located inside housing 200 (see FIGS. 2B-D). For example, controlmodule 210 can turn ON air blower 230 when the temperature in theinterior of structure 150 is lower than the temperature setting and thetemperature inside collector 120. Control module 210 can turn OFF airblower 230, e.g., when (i) the temperature of the incoming air reachesthe temperature setting or (ii) the temperature of the outgoing air islower than the temperature of the incoming air.

Referring to FIGS. 2B-D, housing 200 has an intake chamber 222 thatconnects air-intake register 202 to an input port 228 of air blower 230.In operation, air blower 230 draws air from intake chamber 222 and blowsit into an air supply tube 232 connected to an input port of the solarcollector. The air pressure generated by air blower 230 pushes the airthrough air-supply tube 232 into the solar collector and forces the airto exhaust from an output port of the solar collector to housing 200through an air-return tube 234. An air exhaust chamber 224 of housing200 then directs the air exhausted from air-return tube 234 toair-exhaust register 204. In one embodiment, each of tubes 232 and 234has thermal insulation (not explicitly shown in FIG. 2) that inhibitsheat exchange between the interior and exterior of the tube.

Referring to FIGS. 2B and 2D, a top wall 242 of housing 200 has amovable lip 244 for engaging the sash of the window in which the housingis to be mounted. Housing 200 has a pair of springs 248, each connectedbetween a respective rod 246 attached to lip 244 and an anchor beam 238attached between the side walls of the housing. When housing 200 isplaced on a windowsill, with front panel 206 facing the interior of thehouse, and the sash is pulled down against top wall 242, springs 248pull lip 244 against the interior side of the sash frame, therebylocking the housing in place.

FIGS. 3A-B show perspective three-dimensional views of an inflatablesolar collector 300 that can be used as collector 120 (FIG. 1) accordingto one embodiment of the invention. More specifically, FIG. 3A showscollector 300 in a deployed state, being operatively connected to ahousing 310 that is installed in a sash window 354. Housing 310 isgenerally analogous to housing 110 (FIG. 1) or housing 200 (FIG. 2).FIG. 3B shows an enlarged view of an inner portion of collector 300.

In a typical embodiment, collector 300 is constructed using flexible(e.g., fabric-like) sheets of material. As used herein, the term“flexible” refers to the inherent capability of an object or material toreversibly change its shape, e.g., to be folded and unfolded, to berolled into a relatively tight roll and then unrolled back into asubstantially flat sheet, and/or to be tightly packed into a relativelysmall volume and then unpacked without sustaining irreversiblestructural damage. The flexible sheets used in collector 300 are bondedtogether to form a plurality of chambers that can be inflated anddeflated as appropriate or necessary, e.g., similar to an inflatablemattress or a pool raft. The description of the various chambers ofcollector 300 that is given below corresponds to a fully inflated stateof the collector. In a deflated state, collector 300, as whole, can becompacted, e.g., into a relatively tight roll whose volume does notexceed about 20%, 15%, or 10% of the volume of the collector in thefully inflated state.

Referring to FIG. 3A, collector 300 has a plurality of hooks 322attached to a side seam of the collector. Hooks 322 can be used, e.g.,as indicated in FIG. 3A, to attach collector 300 to tethers 318 in orderto (i) adjust the orientation of the collector for optimum performanceand/or (ii) secure the collector in windy conditions (also see FIG. 1).Collector 300 further has an optional protractor flap 324 that can beused in the process of orienting the collector at a desired tilt angle.The inner portion of collector 300 has an array 328 of parallel tubularchambers 330. One function of tubular chambers 330 is to direct the airflow inside collector 300 so as to ensure optimal heat extraction fromthe collector. Another function of tubular chambers 330 is to create aninternal support structure for collector 300.

Now referring primarily to FIG. 3B, collector 300 has a flexiblepermeable membrane 336 that divides each tubular chamber 330 into anupper semi-cylindrical sub-chamber 334 and a lower semi-cylindricalsub-chamber 338. If there is a pressure gradient across membrane 336,then the membrane allows the air from one semi-cylindrical sub-chamberof tubular chamber 330 to leak or percolate into the othersemi-cylindrical sub-chamber of that tubular chamber. The pertinentcharacteristics of membrane 336 are described in more detail below,primarily in reference to FIG. 4.

An upper wall 332 of semi-cylindrical sub-chamber 334 is made of aflexible airtight material that is transparent to visible light. Manycommonly available polymeric materials, such as films made of vinyl,polyester, and/or polyethylene, have this characteristic. As a result,wall 332 serves as a glazing layer for membrane 336, which serves as anabsorber of solar radiation. In one embodiment, a single sheet offlexible airtight material is used to form walls 332 of all sub-chambers334. More specifically, this single sheet of material is pleated andattached to membrane 336 as indicated in FIG. 3B.

A lower wall 340 of semi-cylindrical sub-chamber 338 is also airtightand comprises a layer of material capable of reflecting back towardmembrane 336 (i) the IR radiation that is emitted by the heated membraneand/or (ii) the visible light transmitted by the membrane. In theinflated state of collector 300, walls 340 form an array of crudeparabolic mirrors. These mirrors help to concentrate the reflected IRradiation and visible light onto membrane 336, improve heat transferfrom the membrane to the air stream, reduce heat losses in thecollector, and increase the efficiency of solar-energy conversion intousable heat. Alternatively or in addition, wall 340 comprises athermally insulating layer that inhibits heat exchange across the wall.Similar to walls 332, walls 340 of all sub-chambers 338 can be formedfrom a single sheet of flexible airtight material, pleated and attachedto membrane 336.

Referring back to FIG. 3A, collector 300 has an outer airtight shell 342that encloses array 328 of tubular chambers 330. When collector 300 isinflated, shell 342 creates a cushion of substantially still air aroundarray 328, which helps to further reduce the unwanted heat losses fromthe array. In addition, shell 342 functions as an adjustable vessel forconveniently handling, positioning, and protecting tubular chambers 330.An upper wall 344 of shell 342 is made of a flexible material that istransparent to visible light, which can be the same as the material ofwall 332. In one embodiment, shell 342 has a wicking patch and awater-drain valve (neither explicitly shown) for removing condensatesfrom the interior of collector 300.

In a representative embodiment, membrane 336 serves as a glazed,transpired absorber of solar radiation, with one or both of walls 332and 344 providing the glazing for the membrane. As used herein the term“transpired absorber” means that the corresponding entity absorbs asignificant portion (e.g., more than 50%) of solar radiation impingingthereupon and allows an air stream to pass therethrough. In analternative embodiment, in addition to serving as a transpired absorber,membrane 336 also serves as an air filter that captures allergens and/orparticulate matter, e.g., particles having a size greater than about 10μm and smaller than about 100 μm. In various embodiments, membrane 336can have (i) a thickness between about 1 and 10 mm and (ii) a porosity,p, greater than about 50% or even greater than about 80%. Herein,porosity p is defined as a ratio of the pore volume within a square inchof membrane 336 to the total volume occupied by that square inch.

FIGS. 4A-E show representative flexible permeable layers 410, 420, 430,440, and 450 that can be used to form membrane 336 according to variousembodiments of the invention. In general, membrane 336 can have one ormore layers selected from layers 410-450. In certain embodiments,membrane 336 might contain two or more layers of the same type separatedby at least one layer of a different type. For example, in oneembodiment, membrane 336 might have one instance of layer 450 sandwichedbetween two instances of layer 430. One skilled in the art willunderstand that, in various embodiments, other layers of varioussuitable materials can be used in addition to or instead of layers410-450 to form membrane 336.

Referring to FIG. 4A, layer 410 comprises a woven fabric or cloth. Asused herein, the term “woven fabric” refers to a sheet of materialproduced by interlacing two or more sets of yarns, fibers, threads,strings, and/or filaments, wherein the elements within the same set aresubstantially parallel to each other, and the elements from twodifferent sets are oriented with respect to each other at apredetermined angle, e.g., 90 degrees. In various embodiments, layer 410might have fibers with a diameter between about 0.1 μm and about 100 μm,or a mixture of fibers of different diameters.

Referring to FIG. 4B, layer 420 comprises a sheet of porous permeablepolymer. More specifically, layer 420 comprises a polymeric matrixhaving a regular or irregular network of interconnected channels,conduits, pores, voids, and cavities that allow air to percolate throughthe layer. Representative examples of porous permeable polymers aresponges and porous solidified foams.

Referring to FIG. 4C, layer 430 comprises a sheet of pin-perforatedmaterial. In various embodiments, the perforation holes can be arrangedin various patterns, regular or irregular, and have the same ordifferent diameters. The material can be a solid polymer or polymericfoam, a woven or non-woven cloth, etc.

Referring to FIG. 4D, layer 440 comprises a non-woven fabric. As usedherein, the term “non-woven fabric” refers to a sheet of fabric-likematerial made from long fibers or filaments that are bonded together bychemical, mechanical, thermal, or solvent treatment, but not by weavingor knitting. A representative example of a non-woven fabric is felt. Ina representative embodiment, layer 440 can be made by mechanicallyentangling various fibers or by pulverizing molten plastic or plasticfilm. In various embodiments, layer 440 might have fibers with adiameter between about 0.1 μm and about 100 μm, or a mixture of fibersof different diameters.

Referring to FIG. 4E, layer 450 comprises a sheet of permeable compositematerial. As used herein the term “composite material” refers to amaterial made from two or more constituent materials havingsignificantly different physical and/or chemical properties, whichconstituent materials remain separate and distinct on a macroscopiclevel within the finished structure. In a representative embodimentshown in FIG. 4E, layer 450 is a sheet of felt impregnated withparticles 452 of activated carbon. When an air stream goes through layer450, particles 452 absorb and/or adsorb allergens, pathogens, and/orodor-causing pollutants, thereby aiding the air-filtering function ofmembrane 336.

FIGS. 5A-B show perspective three-dimensional blow-up views of variousairflow-distribution components that can be used in collector 300 (FIG.3) according to one embodiment of the invention. More specifically, FIG.5A shows a blow-up view, in which an end panel 510 is detached from thefront end of array 328 of parallel tubular chambers 330 (also see FIG.3B). FIG. 5B shows a blow-up view, in which an end panel 540 is detachedfrom the back end of array 328.

Referring to FIG. 5A, end panel 510 has an air-distribution manifold 512and an air-exhaust manifold 522. Air-distribution manifold 512 has aninput tube 532 that can be connected, e.g., to tube 232 of housing 200(see FIG. 2). Air-distribution manifold 512 also has an output port 514that supplies air to and maintains air pressure in outer shell 342 ofcollector 300 (see FIG. 3A). More specifically, when collector 300 isbeing deployed, port 514 supplies air for the inflation of shell 342.After shell 342 is fully inflated and there is no pressure differentialbetween air-distribution manifold 512 and the shell, port 514 seals offthe shell to maintain the corresponding air pressure therein.Air-exhaust manifold 522 has an output tube 534 that can be connected,e.g., to tube 234 of housing 200 (see FIG. 2).

End panel 510 has an airtight barrier 536 that physically separatesmanifolds 512 and 522 from one another, while serving as a shared wallfor these manifolds. When end panel 510 is attached to the front end ofarray 328, barrier 536 is mated with membrane 336, thereby blockingdirect airflow between manifolds 512 and 522. The air stream enteringair-distribution manifold 512 from input tube 532 is divided anddistributed substantially evenly between different semi-cylindricalsub-chambers 334 of array 328. Similarly, the air streams received byair-exhaust manifold 522 from different semi-cylindrical sub-chambers338 of array 328 are merged and directed into output tube 534. As usedherein, the term “substantially evenly” means that the differences inair flux between different sub-chambers 334 does not exceed, e.g., 15%,10%, or even 5%.

Referring to FIG. 5B, end panel 540 has an array of caps 542. When endpanel 540 is attached to the back end of array 328, each cap 542 forms aterminal wall that seals off the corresponding end of tubular chamber330. Note that, in each tubular chamber 330 near cap 542, membrane 336has an air-release port 538. In operation, air-release port 538 injectsa small jet of air into the corresponding semi-cylindrical sub-chamber338 to increase airflow near the back end of array 328. The increase inthe airflow near the back end of array 328 is beneficial because itdecreases variations in heat exchange rates across the length ofmembrane 336, e.g., a difference between the rates at the front and backends of the array, thereby improving the overall heat-transferefficiency.

FIGS. 6A-B schematically show an airflow pattern in a solar-heating unit600 according to one embodiment of the invention. More specifically,FIGS. 6A and 6B shows top and bottom views, respectively, of a collector620 used in solar-heating unit 600. Collector 620 comprises array 328connected between end panels 510 and 540 (see FIG. 5). Solar-heatingunit 600 also has housing 200 (see FIG. 2), to which collector 620 isconnected. Different arrows in FIGS. 6A-B indicate the volumes anddirections of local air fluxes throughout collector 620. Morespecifically, the length and direction of the arrow indicate the volumeand direction, respectively, of the air flux.

Referring to FIG. 6A, the air stream generated by air blower 230 inhousing 200 enters, through tubes 232 and 532, air-distribution manifold512 of end panel 510. Manifold 512 distributes the received air streamsubstantially evenly between different sub-chambers 334 of array 328.The air flux in each sub-chamber 334 gradually decreases as the airmoves toward end panel 540 because the air percolates through membrane336 into the corresponding sub-chamber 338. In one embodiment, thecombined length of tubes 232 and 532 is smaller than about 1 m, or evensmaller than about 0.5 m. The combined length of tubes 234 and 534 issubstantially the same as the combined length of tubes 232 and 532.

Referring to FIG. 6B, the air flux in each sub-chamber 338 graduallyincreases as the air moves from end panel 540 toward air-exhaustmanifold 522 of end panel 510 due to the additional air percolatingthrough membrane 336 from the corresponding sub-chamber 334. Manifold522 collects the air received from different sub-chambers 338. Thecollected air exits collector 620 through tubes 534 and 234.

The airflow pattern indicated in FIG. 6 has certain advantages overother possible airflow patterns when collector 620 is deployed so thatend panel 510 is at a higher elevation above ground than end panel 540.More specifically, the downdraft flow of the unheated air insub-chambers 334 opposes the natural tendency of heated air to rise dueto its relatively high buoyancy. As a result, the heated air is forcedinto sub-chambers 338, which have lower heat losses than sub-chambers334 due to the presence of IR-reflecting and/or thermally insulatinglayers in walls 340 (see FIG. 3B). In addition, substantially all airflowing through collector 620 comes into contact with the underside ofmembrane 336, which is heated by the solar light reflected by the crudeparabolic mirrors formed by walls 340, thereby extracting additionalheat from the membrane. Advantageously, due to all these features ofcollector 620, the efficiency of solar-energy conversion into usableheat in solar-heating unit 600 is relatively high in comparison to otherflat-panel air-heating solar collectors.

Inflatable solar collectors according to various embodiments of theinvention offer one or more of the following advantages over comparableprior-art devices. An inflatable solar collector according to arepresentative embodiment of the invention can be manufactured usinginexpensive, durable, readily available materials. The collector isrelatively easy to deploy and remove as needed. In the collapsed state,the collector occupies a very small volume and can be stored in astorage compartment of the housing, which houses the air blower andeasy-to-operate temperature-control circuitry. The collector is easy toadjust to the surrounding terrain and secure at a desired tilt angle.The collector is inherently resilient to impact and shock. Its smoothexterior shell sheds precipitation and is easy to clean. In addition tosupplying heated air, certain embodiments of the collector can alsoserve as air filters.

As used in this specification, the term “inflatable” refers to an objectthat is capable of (i) swelling or distending with air or gas, (ii)being puffed up, and/or (iii) expanding or increasing significantly insize when pumped with air or gas.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. One of ordinary skill in the art will understand thatairflow patterns that differ from the pattern indicated in FIG. 6 canalso be used in various embodiments of the invention. Various dyes andadditives can be used to optimize the color and/or absorption spectrumof membrane 336 for optimal absorption of solar radiation. Althoughvarious embodiments of the invention have been described in reference totubular chambers 330 having round or circular cross-sections, tubularchambers having other cross-section geometries, e.g., rectangular orrectilinear, can similarly be used. Also, the tubular chambers can bedesigned and arranged so that they are not straight and/or parallel toone another. Various modifications of the described embodiments, as wellas other embodiments of the invention, which are apparent to personsskilled in the art to which the invention pertains are deemed to liewithin the principle and scope of the invention as expressed in thefollowing claims.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value of the value or range.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of theinvention. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

Also for purposes of this description, the terms “couple,” “coupling,”“coupled,” “connect,” “connecting,” or “connected” refer to any mannerknown in the art or later developed in which energy or matter is allowedto be transferred between two or more elements, and the interposition ofone or more additional elements is contemplated, although not required.Conversely, the terms “directly coupled,” “directly connected,” etc.,imply the absence of such additional elements.

The use of terms such as height, length, width, top, bottom, is strictlyto facilitate the description of the invention and is not intended tolimit the invention to a specific orientation. For example, height doesnot imply only a vertical rise limitation, but is used to identify oneof the three dimensions of a three dimensional structure as shown in thefigures. The same applies to other above-indicated terms.

The description and drawings merely illustrate the principles of theinvention. It will thus be appreciated that those of ordinary skill inthe art will be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinvention and are included within its spirit and scope. Furthermore, allexamples recited herein are principally intended expressly to be onlyfor pedagogical purposes to aid the reader in understanding theprinciples of the invention and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the invention, as well as specific examples thereof, areintended to encompass equivalents thereof.

1. A system, comprising: a housing having an air-intake register and anair-exhaust register; and an inflatable solar collector operativelyconnectable to the housing, wherein: the housing comprises an air blowerconfigured to draw air through the air-intake register and direct thedrawn air into a tube connectable to the inflatable solar collector; theinflatable solar collector comprises a first chamber and a secondchamber separated by a flexible permeable membrane; in operation, airpressure generated by the air blower causes the drawn air to flowthrough the tube into the first chamber, percolate through the permeablemembrane into the second chamber, and exhaust from the second chamberthrough the air-exhaust register; the inflatable solar collectorcomprises a plurality of tubular chambers, each divided by the permeablemembrane into a respective first sub-chamber and a respective secondsub-chamber; the first sub-chamber is part of the first chamber; and thesecond sub-chamber is part of the second chamber.
 2. The system of claim1, wherein the housing is adapted to be mounted in an opening of astructure having an interior and an exterior so that (i) the air-intakeregister and the air-exhaust register are located in the interior and(ii) the inflatable solar collector is located in the exterior.
 3. Thesystem of claim 2, wherein: the opening is a sash window; and thehousing comprises a movable lip for engaging a sash of the sash window.4. The system of claim 2, wherein, if the housing is mounted in theopening, then the air blower is located in the exterior.
 5. The systemof claim 1, wherein the inflatable solar collector comprises means forengaging one or more tethers to secure the inflatable solar collector ina desired position.
 6. The system of claim 1, wherein the tube isshorter than about 1 m.
 7. The system of claim 1, wherein: the permeablemembrane is adapted to serve as a transpired absorber of solarradiation; and a flexible wall of the first chamber is adapted to serveas a glazing layer for said absorber.
 8. The system of claim 1, wherein:the permeable membrane is adapted to transmit at least a portion ofsolar radiation impinging thereupon; and a wall of the second chambercomprises a reflective layer adapted to reflect said portion back towardthe permeable membrane.
 9. The system of claim 1, wherein: in aninflated state of the inflatable solar collector, the secondsub-chambers are semi-cylindrical sub-chambers; and walls of saidsemi-cylindrical sub-chambers form an array of crude parabolic minorsadapted to reflect radiation transmitted or emitted by the permeablemembrane back toward the membrane.
 10. The system of claim 1, whereinthe inflatable solar collector comprises an air-distribution manifoldadapted to distribute a stream of air received through the tubesubstantially evenly between the first sub-chambers.
 11. The system ofclaim 1, wherein the inflatable solar collector comprises an end panelhaving (i) an air-distribution manifold adapted to distribute a streamof air received through the tube between the first sub-chambers and (ii)an air-exhaust manifold adapted to collect air from the secondsub-chambers and direct the collected air toward the exhaust register,wherein the end panel comprises an airtight barrier that serves as ashared wall for said manifolds.
 12. The system of claim 11, wherein anedge of the barrier is mated with an edge of the permeable membrane. 13.The system of claim 1, wherein the tubular chambers are parallel to eachother.
 14. The system of claim 1, wherein the inflatable solar collectorcomprises an inflatable shell that encloses the plurality of tubularchambers.
 15. The system of claim 1, wherein, in operation, thepermeable membrane serves as an air filter adapted to perform one ormore of the following: (i) remove particles having a size between about10 μm and about 100 μm from the drawn air; (ii) remove an odor-causingpollutant from the drawn air; and (iii)remove an allergen or a pathogenfrom the drawn air.
 16. The system of claim 1, wherein the permeablemembrane comprises one or more layers selected from a set consisting of:(i) a woven fabric; (ii) a sheet of porous permeable polymer; (iii) asheet of pin-perforated material; (iv) a permeable non-woven fabric; and(v) a sheet of permeable composite material.
 17. The system of claim 1,further comprising: a control module; and one or more temperaturesensors operatively coupled to the control module to provide to thecontrol module one or more temperature readings from correspondinglocations in the system, wherein the control module is adapted to turnON and OFF the air blower based on said one or more temperaturereadings.
 18. The system of claim 1, wherein the inflatable solarcollector is reversibly compactable to occupy a volume that is smallerthan about 15% of the volume of said collector in a fully inflatedstate.
 19. A system, comprising: a housing having an air-intake registerand an air-exhaust register; and an inflatable solar collectoroperatively connectable to the housing, wherein: the housing comprisesan air blower configured to draw air through the air-intake register anddirect the drawn air into a tube connectable to the inflatable solarcollector; the inflatable solar collector comprises a first chamber anda second chamber separated by a flexible permeable membrane; inoperation, air pressure generated by the air blower causes the drawn airto flow through the tube into the first chamber, percolate through thepermeable membrane into the second chamber, and exhaust from the secondchamber through the air-exhaust register; and the housing comprises acompartment for storing the inflatable solar collector in a deflatedstate.